Hot water boiler



FIG. 1 is a top perspective view of a hot water boiler showing our new design;

FIG. 2 is a left side elevation view of the hot water boiler of FIG. 1;

FIG. 3 is a front elevation view of the hot water boiler of FIG. 1;

FIG. 4 is a right side elevation view of the hot water boiler of FIG. 1;

FIG. 5 is a back elevation view of the hot water boiler of FIG. 1;

FIG. 6 is an enlarged top view thereof; and,

FIG. 7 is an enlarged bottom view thereof. 

The ornamental design for a hot water boiler, substantially as shown and described. 